Data blending is referred to as a way of combining data in Tableau. Blending gives a quick and simple way to bring information from multiple data sources into a view. For instance, we have Profit data from SQL database and Profit data in an Excel spreadsheet.

This might look confusing but whenever the data blending is used efficiently, it provides the best way to merge data sources in Tableau. We must also avoid using data blending incorrectly so the Tableau Server won’t be brought down.

Primary and Secondary Sources in Data Blending

There is constantly a primary source and a secondary data source when blending in Tableau. It is important for us to know which is the primary source as it can impact your view. As it is a type of left join, all fields will be included from the primary and related from the secondary.

How to Prepare Data For Data Blending

We will demonstrate using the coffee_chain_data and Office city data. Let’s show you how we brought both our primary and secondary data in. Click on the Data Tab to bring in the Coffee Chain Data.

Then we double click on the Coffee Chain Query data to do an inner join using the other tables we have (Location, factTable, Product), which gives us what we have below.

Now, let’s bring in the second data which is the Office City data. Click on the small drop-down to add a new data source and then bring in the data.

Blending the Data

To proceed with our data blending, we observe we have a common column in these two different data sources. This is the Region column in Office City data source and the Market column in the Coffee chain data source. The first thing is to create a relationship using these common columns in our view. To do that, click on Data Tab → Edit Blend Relationship.

On the Edit Blend Relationship page, click on custom to enable us add our common column. By default, Tableau must have selected state from both columns for us. Ensure we set our Sample Coffee chain as the Primary data source here, then click on OK.

So, we move to our view to do a comparison between sales from the two different data sources, just like what we have below. Note that our primary data source will select common data found in the secondary data source. This will be the data shown in the second view as our secondary. Under our Dimension Pane, we can see the active connection on the state which is in Orange color. Also on our Data Pane, we will find the Primary data source marked as blue and secondary as Orange color.

Limitations Of Tableau Data Blending

We also have some key limitations in data blending. Some of the difficulties we might encounter in data blending include the following:

• Dashboard performance not up to standard when data blending
• Calculations not working with a data blend
• The asterisk when data blending
• Filters not working as expected with a data blend.

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